The properties of polyolefin compositions are desirable for a variety of end use applications, particularly in construction, packaging, automotive and consumer markets. The compositions are useful as pressure sensitive adhesives for paper labels, for sealing tires and as adhesives for assembly of single ply roofing. Recently there is a trend toward the use of curable polyolefin compositions. One benefit of these curable compositions is the ability to prepare solventless compositions which following application and curing exhibit properties similar to those of solvent-based adhesives.
A shortcoming of polyolefin compositions, particularly those that cure by a platinum group metal catalyzed hydrosilation reaction, is their inability to develop strong adhesion to a variety of substrates, particularly glass and certain metals, following curing under commercially feasible conditions of time and temperature. One method for remedying this deficiency is by using primer compositions or adhesion promoting additives containing one or more silanes and/or organosiloxanes with a plurality of silicon-bonded hydrolyzable groups and at least one organofunctional substituent that is bonded to silicon through at least one carbon atom.
Primer compositions are applied to substrates to which adhesion is desired prior to application of a curable composition. Adhesion promoters are present as additional ingredients in curable composition.
U.S. Pat. No. 5,397,648 to Babu et al. describes pressure sensitive compositions for automotive masking tape. The compositions include a moisture curable alpha olefin copolymer containing hydrolyzable or condensable silyl groups.
U.S. Pat. No. 4,981,728 to Homma et al. describes a method for bonding curable organic polymer compositions to a surface using a primer. The curable composition contains 1) an organic polymer with SiX units where X is OH or hydrolyzable group, 2) an epoxy resin, 3) a curing agent for the epoxy resin and 4) a curing agent for the organic polymer. The primer is a vinyl polymer containing Si bonded to OH or hydrolyzable group and is a reaction product of a) a vinyl-containing polymer, preferably a poly(meth)acrylate, and b) a silane or siloxane containing hydrogen and hydrolyzable groups bonded to silicon.
The use of organic or inorganic compounds containing epoxy groups as adhesion promoters for curable organosiloxane compositions is taught in the following prior art:
Polyorganosiloxanes containing epoxy groups and silicon-bonded alkoxy groups at the terminal positions are described in U.S. Pat. No. 5,232,959 to Togashi et al.; PA1 Polyorganosiloxanes containing alkenyl groups with at least 6 carbon atoms and at least one epoxy group are described in U.S. Pat. No. 4,912,188, which issued to Colas et al.; PA1 The combination of an unsaturated alcohol and a polyorganosiloxane containing epoxy or acryloxy groups in combination with silicon-bonded alkoxy groups is described in U.S. Pat. No. 4,906,686 to Suzuki et al.; PA1 Silanes containing silicon-bonded alkenyl or alkenyloxy groups in combination with an epoxy group are described in U.S. Pat. No. 4,732,932 to Waldem et al.; PA1 The combination of a) a polyorganosiloxane containing SiOH and alkenyl groups and b) a silane containing epoxy and silicon-bonded alkoxy groups is described in U.S. Pat. No. 4,087,585 to Schulz; and PA1 U.S. Pat. No. 5,595,826, which issued to Gray and Lutz on Jan. 21, 1997 teaches using the combination of 1) a compound containing at least one epoxy group and 2) a compound containing at least one hydroxyl group and at least one substituent selected from silicon-bonded hydrogen, alkenyl, acryl and methacryl. PA1 1) the platinum group metal-catalyzed reactions of silicon-bonded hydrogen atoms with alkenyl radicals present on the polyolefin; PA1 2) the reaction of ethylenically unsaturated substituents on the polyolefin with mercapto groups in the presence of a catalyst that is typically a metal carboxylate of a chelated organometallic compound such as ferrocene; PA1 3) reactions involving the ethylenically unsaturated substituents present on the polyolefin with either free radicals or cations formed by irradiation of photosensitive compounds with ultraviolet light and PA1 4) reactions involving the ethylenically unsaturated substituents present on the polyolefin that are initiated by high energy particles such as thosc present in electron beams. PA1 A. a polyolefin wherein each molecule contains at least two ethylenically unsaturated substituents capable of reacting to cure said polyolefin; and PA1 B. an effective amount of an adhesion promoter for said polyolefin; wherein the adhesion promoter comprises
Japanese Laid Open Pat. Application 9-316293 published on Dec. 9, 1997 discloses curable compositions comprising 1) a hydrocarbon polymer containing in each molecule at least one ethylenically unsaturated group capable of participating in an hydrosilation reaction; 2) a curing agent containing at least two silicon-bonded hydrogen atoms per molecule; 3) a catalyst for promoting a hydrosilation reaction; 4) a compound referred to as a "silane coupling agent" and 5) an organoaluminum or organotitanium compound. The silane coupling agent is defined as a silane containing at least one alkoxy group and at least one organofunctional group selected from epoxy, methacrylyl, acrylyl, isocyanate, isocyanurate, vinyl and carbamate.